In recent years, novel next-generation electronic materials and devices such as carbon nanotubes, nanowires (semiconductor and metal), phase change memory (PCRAM) circuits, ferroelectric memory (FeRAM) and magnetic random access memory (MRAM) circuits (hereinafter “functional devices” or “functional materials”) have attracted intense interest. These materials and devices can be used for electronic switching and amplification, chemical and environmental sensing, data storage and other applications. For example, MRAM and phase change memory may replace conventional silicon-based electrically erasable programmable memory (EEPROM) and flash memory.
In many cases it is desirable to combine these functional devices with complementary oxide semiconductor (CMOS) integrated circuits. However, there are significant barriers to integrating functional materials with CMOS processing. For example, carbon nanotubes and semiconductor nanowires typically require high temperatures for fabrication and processing. These high temperatures can damage or destroy CMOS circuits, which typically cannot tolerate temperatures above 400 C. Similarly, magnetic thin films, chalcogenide thin films and some metal oxides must be deposited at high temperatures above 400 C to achieve acceptable film quality. Hence, the temperature sensitivity of CMOS circuits precludes fabrication or deposition of these functional materials directly onto CMOS integrated circuits.
Additionally, CMOS circuits can be damaged or destroyed by contamination from metals present in functional device materials, or chemicals necessary for processing functional materials. For example, metals present in phase change materials or magnetic thin films can damage the performance of CMOS circuits if allowed to penetrate the semiconductor junction regions. Hence, integration will require reliable isolation of the CMOS devices from the functional devices. The isolation must prevent diffusion of destructive atomic species.
It would be an advance in the art of microelectronics to provide a method for integrating into CMOS circuits materials that require high temperature processing. Also, it would be an advance in the art to provide a method for integrating novel materials that will not introduce destructive contamination into CMOS circuits. Such a method could be used to create CMOS circuits with integrated functional devices such as carbon nanotubes, semiconductor nanowires, phase change materials, MRAM, PCRAM, FeRAM and magnetic thin films.